1. Field of the Invention
The present invention relates to a node device, communication network system having a plurality of node devices, and control method therefor.
2. Description of the Related Art
In recent years, networks having node devices connected by multiplex transmission paths have been so examined as to cope with high-speed, large-capacity networks for connecting terminal devices along with an increase in information amount.
Some of these networks transmit packets while changing the communication channel in a node device.
An example of this network will be described.
FIG. 11 is a block diagram showing the arrangement of a node device in this network that is connected to terminals 1151 to 1158 via sub-transmission paths.
Reference numerals 1101 to 1108 denote separation/insertion units having a function of detecting the addresses of packets input via parallel multiplex transmission paths, separating the packets into packets to be transmitted to terminals via sub-transmission paths and packets to be input to buffers, and inserting packets transmitted from terminals into packet flows input via the parallel multiplex transmission paths.
Reference numerals 1111 to 1118 denote buffers having a function of temporarily storing packets output from the separation/insertion units in storage areas corresponding to the output terminals of a switch 1141.
Reference numerals 1121 to 1128 and 1131 to 1138 denote parallel multiplex transmission paths for connecting nodes on which a plurality of transmission paths (communication channels) are multiplexed. For example, the parallel multiplex transmission paths 1121 to 1128 and 1131 to 1138 are a plurality of spatially separated optical fiber transmission paths, or wavelength multiplex transmission paths wavelength-divided and multiplexed on one optical fiber.
Reference numeral 1141 denotes a switch controlled by a switch controller 1142 to connect packets input to input terminals IN1 to IN8 to arbitrary output terminals OUT1 to OUT8. The switch 1141 is switched using a space switch or the like when a plurality of optical fiber transmission paths are used for the parallel multiplex transmission paths. When the wavelength multiplex transmission paths are used, transmitters made up of a plurality of tunable laser diodes and multiplexer are connected to the wavelength multiplex transmission paths, and respective wavelengths are demultiplexed by a demultiplexer at the receivers of the wavelength multiplex transmission paths, thereby constituting the switch between nodes, although not shown in FIG. 11. The switch is switched by setting the transmission wavelength of the tunable laser diode to an arbitrary one of wavelengths xcex1 to xcex8.
The switch controller 1142 controls the switch in accordance with, e.g., a control pattern in FIG. 5.
Reference numeral 1143 denotes a buffer controller for controlling to read out a packet stored in the buffer when the input terminal of the switch connected to each buffer is connected to a desired output terminal.
FIG. 5 shows a control pattern representing the connection relationship between the input and output of the switch 1141. The input/output connection relationship of the switch is changed by control addresses A1 to A8. The input terminals IN1 to IN8 correspond to the buffers 1111 to 1118, and the output terminals OUT1 to OUT8 (or transmission wavelengths xcex1 to xcex8) correspond to storage areas 1 to 8 of the buffers.
The communication principle of the network will be explained with reference to FIG. 13. For illustrative convenience, FIG. 13 shows node devices each having four terminals connected to parallel multiplex transmission paths made up of four transmission paths.
This network has a plurality of rings A, B, C, and D, and these rings are connected to each other by switches 1305 to 1308.
Each terminal is connected to one ring transmission path of the parallel transmission paths A, B, C, and D, and when communicating with a terminal connected to another ring, switched at least once to that ring by an arbitrary switch. The switching position is not specified. To facilitate communication control, the terminal is switched to a transmission path connected to a destination terminal at a node immediately preceding the destination node, and switched to an arbitrary transmission path at another node.
To simplify the node device in this network, the switches 1305 to 1308 change the input/output connection relationship in accordance with a specific cyclic pattern every predetermined period regardless of an input signal. Input signals are temporarily stored in buffers 1309 to 1312. When the input/output connection relationship of the switch attains a desired one, packets are read out from the buffers and switched.
For example, when a terminal 1322 communicates with a terminal 1332, a packet output from the terminal 1322 is stored in the buffer 1309 of a node 1301. When the input terminal IN2 of the switch 1305 is connected to, e.g., the output terminal OUT2, the packet is read out from the buffer and output to the transmission path B. When IN2 and OUT4 of the switch 1306 are connected, the packet input to the buffer 1310 of anode 1302 is readout from the buffer, output to the transmission path D, and transmitted to the terminal 1332.
In this way, communication is done by switching to an arbitrary ring transmission path at each node device.
In this network, when a plurality of packets transmitted by a given terminal reach a destination terminal, the packet transmission order of the transmitting terminal may be different from the packet reception order.
This will be described with reference to FIGS. 5, 6, 7, 11, and 12.
In the following description, the parallel multiplex transmission paths are a plurality of spatially separated optical fiber transmission paths, and the switch is a space switch. When the wavelength multiplex transmission paths are used, almost the same operation is done based on the above principle. An example of operation when a terminal 1213 communicates with a terminal 1232 will be explained.
Data transmitted from the terminal 1213 is segmented into fixed-length packets 1, 2, 3, and 4, and each packet is output with a destination address described at its header. Output packets 1, 2, 3, and 4 are input to a node device 1201 via a sub-transmission path, inserted in a packet flow from the parallel multiplex transmission path by the separation/insertion unit 1103, and transmitted to the buffer 1113. Since the destination address of the input packet does not coincide with the address of an adjacent downstream node device, the buffer 1113 stores the packet in an arbitrary storage area. In this case, packets 1, 2, 3, and 4 are respectively stored in storage areas 1, 2, 3, and 4.
The buffer controller 1143 waits for reading out packet 1 until the input terminal IN3 of the switch 1141 is connected to the output terminal OUT1. When the input terminal IN3 is connected to the output terminal OUT1, buffer controller 1143 reads out packet 1. The buffer controller 1143 similarly reads out packets 2, 3, and 4. The switch controller 1142 sequentially supplies control addresses A1, A2, A3, A4, A5, A6, A7, and A8 in accordance with a table shown in FIG. 5 to change the connection relationship of the switch 1141. Further, the switch controller 1142 supplies the control addresses every 1-packet period to control to repeat the same pattern every 8-packet period. The switch controller 1142 informs the buffer controller 1143 of this information, thereby controlling the buffer read timing.
In this example, when the input terminal IN3 of the switch 1141 is connected to the output terminal OUT1, packet 1 is read out from storage area 1 of the buffer 1113, and output to the transmission path 1131 via the output terminal OUT1 of the switch 1141. Similarly, when the input terminal IN3 of the switch 1141 is connected to the output terminal OUT2, packet 2 is read out from storage area 2 of the buffer 1113. When the input terminal IN3 of the switch 1141 is connected to the output terminal OUT3, packet 3 is read out from storage area 3 of the buffer 1113. When the input terminal IN3 of the switch 1141 is connected to the output terminal OUT4, packet 4 is read out from storage area 4 of the buffer 1113. These packets are respectively output to the transmission paths 1132, 1133, and 1134.
FIG. 6 shows this state. Note that the timing relationship in FIGS. 5 and 6 is as follows. The switch controller 1142 outputs to the switch 1141 the control address A7 of the table shown in FIG. 5 in the time period T1, the control address A8 in the time period T2, the control address A1 in the time period T3, and the control address A2 in the time period T4.
Packets 1, 2, 3, and 4 having passed through the transmission paths 1121, 1122, 1123, and 1124, respectively, are input to a node device 1202. Packets 1, 2, 3, and 4 pass through the separation/insertion units 1101, 1102, 1103, and 1104, and are input to the buffers 1111, 1112, 1113, and 1114 in the time periods T2, T3, T4, and T5, respectively (see FIG. 7).
FIG. 7 shows the specific time periods and input channels of packets 1, 2, 3, and 4, and the connection relationship between the input and output channels in each time period. The connection relationship between the input and output channels is changed by changing connection between the input terminal IN and output terminal OUT of the switch 1141, as described above. For example, input channel 1 and output channel 5 are connected by connecting IN1 and OUT5 of the switch 1141.
The buffers 1111, 1112, 1113, and 1114 of the node device 1202 detect the headers to find that each destination address coincides with the address of an adjacent down stream node device. Thus, the buffers 1111, 1112, 1113, and 1114 designate storage areas corresponding to a transmission path connected to the destination terminal. In this example, since the destination terminal is connected to the transmission path 1132, packets 1, 2, 3, and 4 are respectively stored in storage areas 2 of the buffers 1111, 1112, 1113, and 1114.
A read of packets 1, 2, 3, and 4 from the respective buffers in the node device 1202 will be explained. Assume that the output timing of the control address from the switch controller 1142 in the node devices 1201 and 1202 is as follows. When the switch controller 1142 of the node device 1201 outputs the control address A7 in the time period T1, the switch controller 1142 of the node device 1202 outputs the control address A6. That is, the output timing of the control address in the node device 1202 is delayed by the time period T from the output timing of the control address in the node device 1201.
As is apparent from FIG. 7, the connection timings of input channels 1, 2, 3, and 4 to output channel 2 are respectively in the time periods T5, T4, T11, and T10. Therefore, packets 1, 2, 3, and 4 are respectively output from output channel 2 in the time periods T5, T4, T11, and T10, and pass through the transmission path 1132.
That is, packets 1, 2, 3, and 4 are output to a node device 1203 in the order of packets 2, 1, 4, and 3. Since each destination address designates a terminal connected to the separation/insertion unit 1102, packets 2, 1, 4, and 3 input to the separation/insertion unit 1102 of the node device 1203 are separated from the transmission path and output toward the terminal. The packets output from the separation/insertion unit 1102 toward the terminal are received by the terminal 1232 via a sub-transmission path.
As described above, a plurality of packets output from the transmitting terminal may reach a destination terminal in a different order from the transmission order.
It is an object of the present invention to perform communication at high efficiency even in the above network.
It is another object of the present invention to rearrange the order of received packets in a network of performing communication while changing the communication channel.
It is still another object of the present invention to rearrange packets in the packet transmission order, and then transmit them to a destination terminal in a network of performing communication while changing the communication channel.
It is still another object of the present invention to receive packets by a destination terminal with traffic characteristics based on the transmission traffic characteristics of the packet in a network including a communication device for performing communication while changing the communication channel.
It is still another object of the present invention to make the transmission traffic characteristics of the packet equal to reception traffic characteristics at a destination terminal in the network including a communication device for performing communication while changing the communication channel.
It is still another object of the present invention to guarantee QoS (Quality of Service) of ATM, and particularly, CDV (Cell Delay Variation) of QoS in a communication device for performing communication while changing the communication channel.